The global wealth of high-net worth individuals is set to rise from a current $50 trillion (â¬31.7 trillion) to $75 trillion by 2012, although this implies a slow down in the rate of increase, according to consulting firm Oliver Wyman.

In a newly published report on the industry, Wyman, part of US finance group Marsh & McLennan, said the rate of increase was 11% per year over the last five years. But it expects this rate of increase to slow to 9% in the next five, due to less buoyant market conditions.

The Asia-Pacific region and the Middle East are expected to grow by 12% but the global average is likely to be pulled down by the US where growth could fall to 8%.

Wyman believes there are sizable opportunities for advisers to win new business in the years ahead because an estimated 50% of assets held by the wealthy are neither managed nor advised by third parties.

But fee scales vary widely: the average European onshore client generates returns to advisers that are three to four times higher than in the US, where the commission-driven broker/dealer model is dominant.

At large groups, private banks can generate synergies from sister investment bank operations: "But (they) need to restrict potentially harmful activities such as proprietary trading and leveraged finance in order to safeguard against reputational spill-over effects."

Synergies currently contribute 4% to group income at the larger banks, although Wyman warns that shares in lenders with both private and investment banking operations tend to trade at a discount to pure private banks, particularly in the wake of recent market turmoil. The provision of loans to private clients has become important, particularly in emerging markets: "On average, wealth managers generate 12% of revenues from lending."

Growth onshore is expected to be a priority as tax authorities take a tough stance on tax evasion in offshore locations.

This has already taken place in Liechtenstein.

Wyman said: "This trend is likely to extend to other European offshore centers."